A DIY Mini UPS for Wi-Fi Router
Open Green Energy's device uses a TP5100 charging module and LM2587 boost converter.
Anyone using a fixed-line connection has experience with their Wi-Fi dropping when there’s a power outage. This is a huge inconvenience when they’re in an important meeting. Now, Open Green Energy has created a mini UPS for a router that ensures the Internet connection won’t be lost if that should occur.
The circuit in this device operates by drawing power from the mains through a 12V DC adapter, which charges the batteries that will ultimately save the day. Like other battery backups, if the mains power fails, energy stored in the battery powers the router. But, it’s tiny! This unit has a voltmeter, which is pretty useful for measuring the battery voltage level. Both IN5822 diodes block the reverse current flow. The two batteries, which are joined together with double-sided tape, are connected to a 2S BMS board. The board protects the battery pack while it charges and discharges. This battery pack is also wrapped in electrical tape to protect it from metal on metal contact.
The battery positive terminal connects to the LM2587 boost converter IN+ terminal via a rocker switch. Then, the negative terminal is connected to the boost converter IN+ terminal. The LM2587 boost converter Out+ terminal connects to the output DC jack’s positive terminal via a Schottky diode. Out+ terminal connects to the DC jack’s negative terminal.
This device has a TP5100 charging management module to keep the battery pack charged. However, the board can only charge a single battery (4.2V). Open Green Energy soldered the ‘SET’ soldering pad so that the module can charge double batteries (8.4V). Two Schottky diodes are used in this project to prevent reverse current flow as well. Both of the legs were trimmed, and then two pieces of wire were soldered to them. Afterward, heat-shrink tubing was added to the terminal joints.
Open Green Energy designed the enclosure using Autodesk Fusion 360. Next, the parts were printed using the Creality CR-108 printer and 1.75 mm grey and red PLA filaments. The TP5100 charging board, battery pack, and the LM2587 boost converter were mounted using hot glue. Lastly, the boost converter output was set to 12V. It’s kind of cool for the size — worth a build. I just now casually glanced over at a box full of 18650 batteries I would never otherwise use. Hmm…